• Geomechanics and Engineering
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• 제36권1호
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• pp.51-69
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• 2024

Currently, composite lining mountain tunnels in China are generally classified based on the [BQ] method for the surrounding rock grade. Increasingly, tunnel field construction is replicated indoors for scale down model tests. However, the development of analogous materials for model tests of composite lining tunnels with different surrounding rock grades is still unclear. In this study, typical Class III and V surrounding rock analogous materials and corresponding composite lining support materials were developed. The whole processes of excavation-support dynamics of the mountain tunnels were simulated. Data on the variation of deformations, contact pressures and strains on the surrounding rock were obtained. Finally, a comparative analysis between model tests and numerical simulations was performed to verify the rationality of analogous material development. The following useful conclusions were obtained by analyzing the data from the tests. The main analogous materials of Class III surrounding rock are barite powder, high-strength gypsum and quartz sand with fly ash, quartz sand, anhydrous ethanol and rosin for Class V surrounding rock. Analogous materials for rockbolts, steel arches are replaced by aluminum bar and iron bar respectively with both shotcrete and secondary lining corresponding to gypsum and water. In addition, load release rate of Class V surrounding rock should be less than Class III surrounding rock. The fenestration level had large influence on the load sharing ratio of the secondary lining, with a difference of more than 30%, while the influence of the support time was smaller. The Sharing ratios of secondary lining in Class III surrounding rock do not exceed 12%, while those of Class V surrounding rock exceed 40%. The overall difference between the results of model tests and numerical simulations is small, which verifies the feasibility of similar material development in this study.

• 오토저널
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• 제12권2호
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• pp.51-58
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• 1990

According to the developments of various composite materials, it seems to be very important to evaluate the strength and fracture behavior of composite materials. When the composite material is considered as orthotropic material, the characteristic equation of orthotropic material have complex roots. If characteristic roots are equal, the fundamental solutions of BEM become singular ones. This paper analyse the fundamental solutions of the singular problem of orthotropic material using the analogous method to isotropic material.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.276-279
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• 1997

When a magnetostrictive material is exposed to a magnetic field, its geometry changes due to a magnetostrictive effect. The magnetostriction is analogous to the piezoeletricity. The displacement of the magnetostrictive material is proportional to the applied current while that of the piezoelectric material is proportional to the voltage. A magnetostrictive material generates large displacement and higher compressive force compared with a piezoeletric material. These advantages provide a good performance of a vibration isolation of a platform. In this work, it is applied to a driving actuator for vibration isolation of a platform. The properties of a magnetostrictive material are investigated in terms of hysteresis and displacement vs. applied current for a various preload. Modeling of the displacement of the vibration isolating actuator is performed as it behaves as a flow source. A sliding mode controller is designed to demonstrate the ability of the magnetostrictive actuator to reduce the vibration at the platform. The effectiveness of the proposed scheme is demonstrated through experimental works. The experimental results of the vibration of the platform axe presented in terms of time response and frequency response.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.265-269
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• 1999

Polyethylene was modified with silanol groups on its surface by photografting of vinyltrimethoxysilane in vapor phase by using benzophenon as a polymerization initiator and by hydrolyzing the methoxysilane groups into the silanol groups with HCI solution. The modified polyethylene formed a dense and homogeneous apatite layer on its surface in a solution with ion concentrations 1.5 times those of human blood plasma within 21 days. This kind of biomimetic process could provide techniques for fabricating apatite-polymer composites with three dimensional structure analogous to the natural bone.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.881-886
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• 2003

Vibration control of plates with a passive electrical damper is presented in this paper. This electrical absorber, piezoelectric patches connected with a resistor and an inductor in series, is analogous to the damped mechanical vibration absorber. For estimating the effectiveness of piezoelectric absorber, the governing equations of motion are derived using a classical laminate plate theory and Hamilton principle. The developed theoretical analyses are validated experimentally for simply-supported aluminum plates in order to demonstrate the performance of passive electrical damper. The result shows that the vibration amplitude is reduced about 14dB for the targeted first vibration mode.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1778-1784
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• 2003

Vibration control of plates with a passive electrical damper is presented in this paper. This electrical absorber, piezoelectric patches connected with a resistor and an inductor in series, is analogous to the damped mechanical vibration absorber. For estimating the effectiveness of piezoelectric absorber, the governing equations of motion are derived using a classical laminate plate theory and Hamilton principle. The developed theoretical analysis is validated experimentally for a simply-supported aluminum plate in order to demonstrate the performance of passive electrical damper. The result shows that the vibration amplitude is reduced about 14dB for the targeted first vibration mode.

• 한국정밀공학회지
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• 제20권6호
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• pp.138-144
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• 2003

A crack in a ferroelectric ceramic subjected to an electric field is analyzed. The boundary of the electrical saturation zone is estimated based on the finite-width saturation zone model, which is analogous to a finite-width Dugdale zone model for mode III. It is shown that the shape and size of the switching zone depends strongly on the boundary of the electrical saturation zone and the ratio of the coercive electric field to the yield electric field. The crack tip stress intensity factor under small scale conditions is evaluated by employing the model of electric nonlinear domain switching. It is found that fracture toughness of the ferroelectric material may be increased or decreased depending on the material property of electrical nonlinearity.

• 대한기계학회논문집
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• 제15권1호
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• pp.179-189
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• 1991

본 연구에서는 특성근이 같은 같은 경우의 기본해 유도에서 사용하였던 상사 방법을 이용하여, 균열끝 부근의 응력장과 변위장을 나타내고자 한다. 위의 해석을 바탕으로 개발한 프로그램의 정도에 대하여 검증하고, 이 프로그램을 복합재료 내의 균열 문제에 응용하여 응력확대계수에 관한 자료를 계산하고, 그 유용성을 검토하고자 한다.

• Composites Research
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• 제12권2호
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• pp.1-9
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• 1999

외부 회로가 연결된 압전 재료는 외부 회로의 영향으로 진동수에 영향을 받는 강성(stiffness)과 손실 계수(loss factor)를 가지게 된다. 일반적으로 외부 회로는 두 종류로 구별이 된다. 저항만으로 구성된 경우와 저항과 인덕터(inductor)로 구성된 경우이다. 저항만으로 구성된 경우를 RES(resistive shunting)라 하는데, 이 경우는 압전 재료의 물성이 점탄성 물질과 비슷하게 진동수에 영향을 받는다. 그러나 점탄성 물질에 비해서 더 큰 강성을 지니고, 온도에 영향을 덜 받는다. 저항과 인덕터로 구성된 경우를 RSP(resonant circuit shunting)라 하는데, PMD(proof mass damper)와 비슷한 방법으로 구조물의 공진을 최적으로 조절할 수 있다. 본 논문에서는 이러한 외부 회로와 연결된 압전 재료를 이용하여 복합재 보의 진동을 수동적으로 제어하는 실험을 수행하여 그 결과를 제시하였다.

• Journal of Applied Biological Chemistry
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• 제52권3호
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• pp.93-102
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• 2009

Polyunsaturated fatty acids (PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have significantly beneficial effects on health in relation to cardiovascular, immune, and inflammatory conditions and they are involved in determining the biophysical properties of membranes as well as being precursors for signaling molecules. PUFA biosynthesis is catalyzed by sequential desaturation and fatty acyl elongation reactions. This aerobic biosynthetic pathway was thought to be taxonomically conserved, but an alternative anaerobic pathway for the biosynthesis of PUFA is now known to contain analogous polyketide synthases (PKS). Certain fish oil can be a rich source of PUFA although processed marine oil is generally undesirable as food ingredients because of the associated objectionable flavors that are difficult and cost-prohibitive to remove. Oil-seed plants contain only the 18-carbon polyunsaturated fatty acid alpha-linolenic acid, which is not converted in the human body to EPA and DHA. It is now possible to engineer common oilseeds which can produce EPA and DHA and this has been the focus of a number of academic and industrial research groups. Recent advances and future prospects in the production of EPA and DHA in oilseed crops are discussed here.